Laura T Lam

Ibrutinib in combination with rituximab in relapsed or refractory mantle cell lymphoma: a single-centre, open-label, phase 2 trial

BACKGROUND Ibrutinib is approved in the EU, USA, and other countries for patients with mantle cell lymphoma who received one previous therapy. In a previous phase 2 study with single-agent ibrutinib, the proportion of patients who achieved an objective response was 68%; 38 (34%) of 111 patients had transient lymphocytosis. We hypothesised that adding rituximab could target mantle cell lymphoma cells associated with redistribution lymphocytosis, leading to more potent antitumour activity. METHODS Patients with a confirmed mantle cell lymphoma diagnosis (based on CD20-positive and cyclin D1-positive cells in tissue biopsy specimens), no upper limit on the number of previous treatments received, and an Eastern Cooperative Oncology Group performance status score of 2 or less were enrolled in this single-centre, open-label, phase 2 study. Patients received continuous oral ibrutinib (560 mg) daily until progressive disease or unacceptable toxic effects. Rituximab 375 mg/m(2) was given intravenously once per week for 4 weeks during cycle 1, then on day 1 of cycles 3-8, and thereafter once every other cycle up to 2 years. The primary endpoint was the proportion of patients who achieved an objective response in the intention-to-treat population and safety assessed in the as-treated population. The study is registered with ClinicalTrials.gov, number NCT01880567, and is still ongoing, but no longer accruing patients. FINDINGS Between July 15, 2013, and June 30, 2014, 50 patients were enrolled. Median age was 67 years (range 45-86), and the median number of previous regimens was three (range 1-9). At a median follow-up of 16·5 months (IQR 12·09-19·28), 44 (88%, 95% CI 75·7-95·5) patients achieved an objective response, with 22 (44%, 30·0-58·7) patients achieving a complete response, and 22 (44%, 30·0-58·7) a partial response. The only grade 3 adverse event in >=10% of patients was atrial fibrillation, which was noted in six (12%) patients. Grade 4 diarrhoea and neutropenia occurred in one patient each. Adverse events led to discontinuation of therapy in five (10%) patients (atrial fibrillation in three [6%] patients, liver infection in one [2%], and bleeding in one [2%]). Two patients died while on-study from cardiac arrest and septic shock; the latter was deemed possibly related to treatment. INTERPRETATION Ibrutinib combined with rituximab is active and well tolerated in patients with relapsed or refractory mantle cell lymphoma. Our results provide preliminary evidence for the activity of this combination in clinical practice. A phase 3 trial is warranted for more definitive data. FUNDING Pharmacyclics LLC, an AbbVie Company.

B-Cell Lymphoma Patient-Derived Xenograft Models Enable Drug Discovery and Are a Platform for Personalized Therapy

Purpose: Patients with B-cell lymphomas often relapse after frontline therapy, and novel therapies are urgently needed to provide long-term remission. We established B-cell lymphoma patient-derived xenograft (PDX) models to assess their ability to mimic tumor biology and to identify B-cell lymphoma patient treatment options. Experimental Design: We established the PDX models from 16 patients with diffuse large B-cell lymphoma, mantle cell lymphoma, follicular lymphoma, marginal zone lymphoma, or Burkitt lymphoma by inoculating the patient tumor cells into a human bone chip implanted into mice. We subjected the PDX models to histopathologic and phenotypical examination, sequencing, and drug efficacy analysis. Primary and acquired resistance to ibrutinib, an oral covalent inhibitor of Bruton tyrosine kinase, were investigated to elucidate the mechanisms underlying ibrutinib resistance and to identify drug treatments to overcome resistance. Results: The PDXs maintained the same biological, histopathologic, and immunophenotypical features, retained similar genetic mutations, and produced comparable drug responses with the original patient tumors. In the acquired ibrutinib-resistant PDXs, PLC-γ2, p65, and Src were downregulated; however, a PI3K signaling pathway member was upregulated. Inactivation of the PI3K pathway with the inhibitor idelalisib in combination with ibrutinib significantly inhibited the growth of the ibrutinib-resistant tumors. Furthermore, we used a PDX model derived from a clinically ibrutinib-relapsed patient to evaluate various therapeutic choices, ultimately eliminating the tumor cells in the patients peripheral blood. Conclusions: Our results demonstrate that the B-cell lymphoma PDX model is an effective system to predict and personalize therapies and address therapeutic resistance in B-cell lymphoma patients. Clin Cancer Res; 23(15); 4212–23. ©2017 AACR.

ATM mutation and radiosensitivity: An opportunity in the therapy of mantle cell lymphoma

ATM (ataxia telangiectasia mutated) is a DNA damage signaling-initiation kinase which has diverse function in responding to genotoxic stress to maintain its genomic integrity. Cells harboring loss-of-function ATM deficiencies demonstrate extreme radiosensitivity. The scope of radiotherapy has been considered very limited among patients with biallelic mutations or deletions of ATM due to its toxic effect on normal tissue. Mantle cell lymphoma (MCL) is a highly chemo-refractory tumor with generally poor outcome, especially if the patients develop resistance to frontline drugs. ATM is the most frequently mutated gene in MCL and recent experimental evidence demonstrated that this mutational status can be taken advantage of using radiotherapy. Radiotherapy should be considered in the treatment of mantle cell lymphoma with a curative intent.

Gene mutations and actionable genetic lesions in mantle cell lymphoma

Mutations and epigenetic alterations are key events in transforming normal cells to cancer cells. Mantle cell lymphoma (MCL), a non-Hodgkins lymphoma of the B-cell, is an aggressive malignancy with poor prognosis especially for those patients who are resistant to the frontline drugs. There is a great need to describe the molecular basis and mechanism of drug resistance in MCL to develop new strategies for treatment. We reviewed frequent somatic mutations and mutations involving the B-cell pathways in MCL and discussed clinical trials that attempted to disrupt these gene pathways and/or epigenetic events. Recurrent gene mutations were discussed in the light of prognostic and therapeutic opportunity and also the challenges of targeting these lesions. Mutations in the ATM, CCND1, TP53, MLL2, TRAF2 and NOTCH1 were most frequently encountered in mantle cell lymphoma. Translational models should be built that would assess mutations longitudinally to identify important compensatory, pro-survival and anti-apoptic pathways and actionable genetic targets.

Strategic therapeutic targeting to overcome venetoclax resistance in aggressive B-cell lymphomas

Purpose: B-cell lymphoma-2 (BCL-2), an antiapoptotic protein often dysregulated in B-cell lymphomas, promotes cell survival and provides protection from stress. A recent phase I first-in-human study of the BCL-2 inhibitor venetoclax in non-Hodgkin lymphoma showed an overall response rate of 44%. These promising clinical results prompted our examination of the biological effects and mechanism of action underlying venetoclax activity in aggressive B-cell lymphoma, including mantle cell lymphoma (MCL) and diffuse large B-cell lymphoma (DLBCL). Experimental Design: MCL and DLBCL cell lines, primary patient samples, and in vivo patient-derived xenograft (PDX) models were utilized to examine venetoclax efficacy. Furthermore, the mechanisms underlying venetoclax response and the development of venetoclax resistance were evaluated using proteomics analysis and Western blotting. Results: Potential biomarkers linked to venetoclax activity and targeted combination therapies that can augment venetoclax response were identified. We demonstrate that DLBCL and MCL cell lines, primary patient samples, and PDX mouse models expressing high BCL-2 levels are extremely sensitive to venetoclax treatment. Proteomics studies showed that venetoclax substantially alters the expression levels and phosphorylation status of key proteins involved in cellular processes, including the DNA damage response, cell metabolism, cell growth/survival, and apoptosis. Short- and long-term exposure to venetoclax inhibited PTEN expression, leading to enhanced AKT pathway activation and concomitant susceptibility to PI3K/AKT inhibition. Intrinsic venetoclax-resistant cells possess high AKT activation and are highly sensitive to PI3K/AKT inhibition. Conclusions: These findings demonstrate the on-target effect of venetoclax and offer potential mechanisms to overcome acquired and intrinsic venetoclax resistance through PI3K/AKT inhibition. Clin Cancer Res; 24(16); 3967–80. ©2018 AACR.

Abstract 3651: Preclinical examination of the effects of MT-3724, an engineered toxin body targeting CD20, in mantle cell lymphoma

Mantle cell lymphoma (MCL) accounts for 6-8% of all non-Hodgkin lymphoma cases and is a therapeutic challenge. MCL is characterized by the expression of different B-cell markers such as CD-19, CD-20 and BSAP/PAX5, and CD-20 is strongly expressed and can be used as a potential target. MT-3724 was developed by Molecular Templates and is an engineered toxin body (ETB) targeting CD-20. MT-3724 binds CD-20 and forces its own internalization into the target cell where it subsequently self-routes to the cytosol to enzymatically and permanently inhibit protein synthesis via ribosome inactivation. By selectively and specifically targeting CD20-positive cells, MT-3724 may decrease cell proliferation and induce apoptosis in MCL. We tested the effects of MT-3724 by in vitro cell proliferation in 3 ibrutinib-sensitive cell lines and 5 ibrutinib-resistant cell lines (4 primary resistant and 1 acquired resistant). We also measured the levels of apoptotic cells in both ibrutinib-sensitive and -resistant cell lines treated with MT-3724 by Annexin V/ PI staining. Lastly, we conducted an in vivo efficacy assay of MT-3724 in a MCL PDX model resistant to a wide-range of drugs, including ibrutinib. MT-3724 inhibited cell proliferation effectively and efficiently in most ibrutinib-sensitive and ibrutinib-resistant cell lines in a dose-dependent manner. IC50 500 ng/ml was considered resistant to MT-3724. Regarding the ibrutinib-sensitive cell lines, the 3 cell lines (Jeko-1, Mino and Rec-1) were sensitive to MT-3724 with IC50 values of 139.1, 309.3 and 457.7 ng/ml, respectively. Regarding the ibrutinib-resistant cell lines, 4 cell lines (Maver-1, JVM-13, Jeko-R and Granta519) were sensitive to MT-3724 with IC50 values of 124.6, 155.1, 266.2 and 442.4 ng/ml, respectively, and 1 cell line (Z-138) was resistant to MT-3724 (IC50 = 1231 ng/ml). However, no significant differences in IC50 values were found between ibrutinib-sensitive and -resistant cell lines (p = 0.36). In a time-dependent assay, 300 ng/ml MT-3724 also reduced cell proliferation in 2 ibrutinib-sensitive cell lines (Mino and Jeko-1) and 2 ibrutinib-resistant cell lines (Jeko-R and Maver-1) over time. Furthermore, MT-3724 also induced cell apoptosis in both ibrutinib-sensitive (Jeko-1) and -resistant (Jeko-R and Maver-1) cell lines. Lastly, MT-3724 was administered intraperitoneally for three consecutive weeks in a PDX model resistant to a wide-range of targeted agents. Interestingly, MT-3724 dramatically reduced tumor burden and increased survival (median of 27 days) of the PDX mice. MT-3724 is the first toxin engineered body targeting CD-20 used in MCL, which may be a potential therapeutic candidate for MCL, especially for drug-resistant cases. Citation Format: Shengjian Huang, Taylor Bell, Yang Liu, Hui Guo, Carrie Li, Makhdum Ahmed, Laura Lam, Hui Zhang, Zhihong Chen, Michael L. Wang, Leo Zhang, Krystle Nomie. Preclinical examination of the effects of MT-3724, an engineered toxin body targeting CD20, in mantle cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3651. doi:10.1158/1538-7445.AM2017-3651